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So you put two guppies in a tank together and one killed the other? How big was the tank? As noted above it's a sign if stress in fish, either the tank wasn't big enough, or the water parameters weren't right. Guppies aren't that territorial, something you're doing isn't right

So you put two guppies in a tank together and one killed the other? How big was the tank? As noted above it's a sign if stress in fish, either the tank wasn't big enough, or the water parameters weren't right. Guppies aren't that territorial, something you're doing isn't right

ya water was probably off because ive had a few guppies in this tank before for a limited time and now that i have 3 smaller ones in it to test it theyre fine but its a small 1.5 cube for fish fry to get big enough to be in my ten gallon without being eaten... i know its small for adults but they are only going to be in there for a week or so so the water can cycle quicker and better its not a new tank or anything but i threw in some small grain gravel so i can put in plants to oxygenate the water so im just trying to get some good bacteria in the substrate before i let my 30+ guppy fry in there... could it have been the reality that it is a small space and theres only two?

Mollies are breeder fish and they are known to breed FREQUENTLY. However, before considering on killing the fries, you should suggest the positive effects first. First off, mollies are small fish ranging from 1'" to 4"(inches) depending on the species that you have. Meaning that a 10 gallon tank is a fairly good housing tank for them. The maximum amount of mollies I would suggest, if it is the only fish your planning to have in the tank, is around 20 or less since they are small. It is usual to have many small fish in the tank. Second, NOT all fish live forever. So, when your mollies die, how are you going to replenish your fish tank other than buy more. My point is that you should look at both the positive and negative sides before considering on killing them. My other suggestion would be to give some of the fish you don't want away like to your neighbors. Hope this helps